The surfactant material which lines the alveolar surface of the lung has been found to contain lipoproteins. The phospholipids of these lipoproteins possess the surface-active properties necessary for normal lung function. The purpose of this research is to identify factors which regulate normal lipid metabolism in the lung. Isolated perfused rat lung will be used to study the pathway of synthesis of lung lipids and specifically the lipoproteins of the surfactant fraction. The dependence of lipid metabolism on carbohydrate metabolism in the lung and the extent to which carbohydrate metabolism regulates surfactant synthesis will be determined. As the lung has now been found to be an insulin sensitive organ, the effect of diabetes on surfactant synthesis will continue to be investigated. These studies will also include measurement of cyclic nucleotide concentration in the normal and diabetic lung and in the perfused lung treated with agents known to alter cyclic nucleotide levels. The effect of changes in cyclic nucleotide levels on surfactant synthesis and secretion will be determined. Other studies will be directed toward determining the role of phosphatidylglycerol found in surfactant material and the subcellular site of the synthesis of the disaturated phospholipids of the surfactant. The precursor-product relationship of the phospholipids and their apoproteins of the lamellar bodies and the same components of the secreted surfactant material will be investigated.